Sorry for the delay in replying.
I used to do some work for a corporation supplying standard ship fittings - I’m an industrialist by nature. I’m fairly high skilled, and while a lot of things I could make it was more effective to make “the most profitable things” and use those profits to buy the items I want.
I have 15m ISK.
I want item A that costs 1m ISK to make and sells on the market for 1.1m ISK. I can buy 13 or make 15.
I make Item B. That costs 2m ISK to make and sells for 2.6m ISK. I turn my 15m ISK into 18.2m ISK, then I can buy 17 of the item A I want.
Making item B gives me more of Item A.
There may be a satisfaction if flying a ship you built yourself (and I can see that) but sometimes you have to shake the dead hand of economics for an objective of maximising output.
Anyway, Uncle Terak is rambling.
I’ve looked at bulk reprocessing as a business opportunity in the past: I’ve maximum reprocessing skills, access to a good refinary and it’s still a marginal business. Set up buy orders somewhere where people mine (rookie systems - I was going to make a fair offer, drive the prices up a bit there to stop new players being a bit ripped off) - but the haulage was going to be a pain, especially given the physical volume of the ore. Others may find space-trucking fun: to me it’s an unfortunate fact of life. I find industry fun, combat less so. But that’s Eve: Allsorts in the bag - rip the head off Bertie if you don’t like how he tastes.
As a small corporation:
If you use an NPC station to refine, buy or sell, or manufacturer then look at the activity indexes, get good standings with that NPC corporation, train up the relevant refining and trade skills. All the little 2% and 0.1% offs add up to a competitive edge.
NPC stations are never as advantageous as a player owned station. But they are low hassle and less risk (you are paying a premium for that).
You can set up a nice refinary of your own somewhere off the beaten track. But if you own it you have to deal with all the associated liabilities - fueling it, capital investment for it and it’s fittings, a core. And defending it or replacing it when someone wants to kick it over.
Or you can talk to another group and negotiate favourable rates for using their refinary - a lot of places will give you a lower tax rate just for regular business, or if you are willing to help them defend their stations. Or you could offer yourselves as help to their manufacturing wing.
Maintain a modicum of independence, but work with a group.
Is it worthwhile?
I like making things. I sell them at a profit - optimising the supply chain, reading the market for opportunities really floats my boat. I can be happy as a soloist (and the market has been good to me recently - weird good).
Ultimately, it’s what makes you content.
And that’s different for different people.
For an industrialist/manufacturer there is a lot to offer in New Eden - it’s a matter of making it work for you.